Question
Hi,
I have a mature 50+ ft cottonwood which normally loses its leaves in early Sept.  This year it started to lose them in earnest Aug 5th and is losing them as it would normally in Sept.  We have had a very wet spring and periods of hot dry weather in summer.  However we have had flash storms that have left standing water near the tree 6 times this summer for a day or so.  I live in the western suburbs of Chicago.  Do you think its stressed or something more serious.

Answer
I think the stress of too much water that stood around the roots for more than a day would cause the leaves to drop prematurely. I would not really worry about the dropping early. The tree will soon start shutting down the growth and next year it should leaf out fine and you should not be able to see any difference in the amount of foliage from this spring. Does not sounds like anything to worry about.